Hi,
as agreed with Nathaniel, we should change the defaults of krb_use_fast
to "try" with the IPA backend and also change the default of
krb5_fast_principal to "host/$client_hostname".
So far I've tested this patch on F-20 only with IPA server
3.3.90GIT0f82cbf. More testing is needed with older IPA servers as well,
but that shouldn't block the patch review.